1. Field of the Invention
The present invention relates to a patterned master medium (“master”) that is used to write servo information by a magnetic transfer method (magnetic contact duplication) to a vertical magnetic recording medium. The present invention also relates to a method for formatting a vertical magnetic recording medium by using such a magnetic transfer method.
2. Description of the Related Art
As information processing volumes of computer systems increase, magnetic recording media constituting storage devices such as hard disks are confronted by demands for an increased storage capacity. Vertical magnetic recording-type magnetic recording media have attracted attention in recent years as media capable of fulfilling such demands.
FIGS. 29 and 30 show a magnetic disk 200, which is an example of a vertical magnetic recording-type magnetic recording medium. FIG. 29 is a plan view of the constitution of the recording face of the magnetic disk 200, and FIG. 30 shows the laminated constitution of the magnetic disk 200.
As shown in FIG. 30, the magnetic disk 200 has a laminated structure that consists of a substrate 201, a magnetic recording layer 202, a soft magnetic layer 203, an intermediate layer 204, and a protective film 205. The magnetic recording layer 202 is a vertical magnetization film, and allows a predetermined signal to be recorded as a change in the magnetization direction. Such a magnetic recording layer 202 constitutes the recording face of the magnetic disk 200. The soft magnetic layer 203 consists of a soft magnetic material. The intermediate layer 204 consists of a nonmagnetic material and magnetically separates the magnetic recording layer 202 and soft magnetic layer 203. The protective film 205 physically and chemically protects the magnetic recording layer 202 from the external environment while securing a lubricating ability for the medium surface with respect to a record/playback magnetic head.
A plurality of concentric information tracks 210 as shown in FIG. 29 (partially omitted) are magnetically constituted in the magnetic recording layer 202 that constitutes the recording face of the magnetic disk 200. The magnetic recording layer 202 is divided into servo zones 202A and user data zones 202B in the direction of extension of the film face. The servo zones 202A are areas in which predetermined servo information for controlling the alignment of the record/playback magnetic head with the magnetic disk 200 with respect to a target information track 210 is recorded. The user data zone 202B is a part that allows user data to be recorded in respective information tracks 210 such that the user data can be rewritten.
In the fabrication of a magnetic disk 200 of this kind, the soft magnetic layer 203, intermediate layer 204, magnetic recording layer 202, and protective film 205 are first sequentially formed on the substrate 201. Each of these layers and film is formed by depositing a predetermined material by sputtering, for example. Next, servo information is recorded in the magnetic recording layer 202 to form the servo zones 202A.
The magnetic transfer method is known as one procedure for recording servo information. FIG. 31 shows a series of steps in a case where servo information is recorded by a conventional magnetic transfer method in the process of fabricating the magnetic disk 200. In this method, as shown in FIG. 31A, initial magnetization of the magnetic recording layer 202 of the magnetic disk 200 is first performed. More specifically, by applying an initial magnetization magnetic field H1 in a predetermined direction, the magnetization direction of the magnetic recording layer 202 can be kept uniform. With a view to simplifying the illustration, layers and films of the magnetic disk 200 other than the substrate 201 and magnetic recording layer 202 are omitted from FIG. 31. Next, as shown in FIG. 31B, a magnetic transfer master 300 and the magnetic disk 200 are overlapped. The master 300 comprises a substrate 301, and a magnetic material pattern 302 formed as a pattern on the substrate 301. The magnetic material pattern 302 consists of a soft magnetic material, for example, that has high magnetic permeability. Further, the magnetic material pattern 302 has a pattern shape that corresponds with desired servo information that is to be recorded in the magnetic recording layer 202 of the magnetic disk 200. Next, as shown in FIG. 31C, the pattern shape of the magnetic material pattern 302 is transferred magnetically to the magnetic recording layer 202. More specifically, by applying a transfer magnetic field H2 in a direction that is the reverse of the above initial magnetization magnetic field H1 to the master 300 and magnetic disk 200, the magnetization direction at points in the magnetic recording layer 202 that face the magnetic material pattern 302 is reversed. Therefore, servo information is recorded in the magnetic recording layer 202 to form the servo zones 202A. Conventional magnetic transfer methods are described in Japanese Patent Application Laid Open Nos. H10-320768 and 2003-173513, for example.
After the servo zones 202A have been formed, with servo information recorded, user data can be recorded on the magnetic disk 200. More specifically, while the alignment of a predetermined magnetic head comprising a write head element is controlled with respect to the recording face of the magnetic disk 200 (magnetic recording layer 202) by using the servo information, predetermined data can be recorded in the user data zones 202B between the servo zones 202A by the magnetic head.
When information tracks 210 are formed by recording user data in the user data zones 202B of the magnetic disk 200 where servo information has been written by the above conventional magnetic transfer method, intertrack portions 211, in which the magnetization direction is kept uniform, are produced in the user data zones 202B as shown in FIG. 32. FIG. 32 shows a partial cross-section of the magnetic disk 200 in the radial direction of the magnetic disk 200, that is, in a direction that transects the information tracks 210. Between the respective information tracks 210 constituted by user data, the magnetization direction of the magnetic recording layer 202 is kept in the direction of the initial magnetization of the above magnetic transfer method. Because the intertrack portions 211 are magnetized uniformly in the initial magnetization direction, a comparatively strong magnetic field that originates in the intertrack portions 211 is formed near the surface of the medium. When the magnetic disk 200 is played back, the magnetic field acts on the record/playback magnetic head RW as a non-signal magnetic field (disturbance magnetic field) and affects the reading operation of the magnetic head RW. More specifically, the non-signal magnetic field that originates in the intertrack portions 211 acts on the read head element for reading that is mounted on the magnetic head RW and affects the playback signal outputted by the read head element. Because the non-signal magnetic field thus originating in the intertrack portions 211 is strong, it is difficult to obtain a favorable playback characteristic for the magnetic disk 200.